This invention relates to a process for heating solids to prepare them for subsequent processing and is particularly concerned with a process for preheating carbon-containing solids such as oil shale and coal in a transfer line prior to subjecting the carbon-containing solids to a conversion process such as oil shale retorting or coal gasification.
In the retorting of oil shale and in the gasification of coal, the carbon-containing feed material must be heated to high temperatures in order for the desired reactions to occur. The major heat load required in these processes is for heating the feed material to reaction temperatures. In order to efficiently supply this heat, it is common practice to preheat the carbon-containing feed material to a temperature below reaction temperature before introducing it into the reaction zone. Normally, the preheating is carried out by contacting all of the feed solids with hot gases produced in the conversion process. Unfortunately, such a preheating process normally results in loss of yield in the subsequent conversion process even though the preheating is conducted at temperatures below the normal reaction temperature. This premature loss of yield not only results in loss of valuable products in the conversion process but also can contribute to pollution problems because of the presence of hydrocarbons and other contaminants in the gases that are normally vented from the preheater into the atmosphere.